Some organisms get an unfair reputation, in particular within groups like insects. The beetle 𝘖𝘤𝘺𝘱𝘶𝘴 𝘰𝘭𝘦𝘯𝘴 (O.F.Müller, 1764) is one of them as it has been associated with devil, hence its common name- Devil’s coach horse beetle. This name, forged from medieval superstitions, is as remarkable as its appearance. Today, let’s bring back some justice and reveal the secrets behind this majestic creature.
The Devil's coach horse beetle is a common and widespread species native to Europe and North Africa. They have also been introduced accidentally to the Americas around 1926. Adult sizes range from 20 to 32 millimeters, with the Devil’s coach horse beetles among the largest beetles in the Staphylinidae family, also known as Rove beetles. Staphylinidae is one of the oldest families within the order Coleoptera (beetles), with the oldest record tracing back to the Triassic era (252-201 million years ago ). These beetles are typically uniformly black with strong mandibles and short wing covers that leave their powerful abdomen exposed. Although capable of flight, the Devil’s coach horse beetle rarely takes to the air. Instead, it primarily inhabits woodlands, residing beneath stones or organic materials. Both larvae and adults of the beetles are versatile predators that are active at night. They feed on a range of invertebrates including worms, slugs, caterpillars and beetles.
When late Summer to early Autumn approaches , reproduction is in the air (or on the ground). Two to three weeks after mating, females lay eggs in dark and damp places under stones, moss or litter. The white, straw-coloured head larvae emerge after 30 days and live mainly underground. They present similar well-developed mandibles as the adults. At around 150 days old, the larvae pupate for a period of about 35 days and then emerge into their adult form. Adults can survive through a second winter, with some individuals even living up to two years!
What is the origin of such a peculiar name? The Devil's coach horse beetle is surrounded by a number of myths and superstitions, one of which being its supposed ability to curse a person by pointing its raised abdomen in their direction. This belief may have been inspired by its behaviour of jaws opening associated with the curling up of its abdomen like the tail of a scorpion when threatened. If the threat persists, the beetle will protrude white vesicles from the tip of its abdomen, emitting a foul-smelling odor as a chemical repellent. In fact, the species name epithet “olens” means “smelling”, and is derived from the stinking smell emitted by the beetle. Although they are non-venomous, they can still produce painful bites using their powerful mandibles.
Similarly to other rove beetles, the Devil’s coach horse beetle is a fast-moving organism allowing it to actively prey on many invertebrates. Once the prey is subdued, it is secured with its mouthparts and firm grip of its first and second pairs of legs. The mandibles are very effective in tearing the prey apart and an adult can consume almost its weight in food daily. What a big eater!
In addition to their strength, the Devil’s coach horse beetles are also clever predators that are able to discriminate between suitable prey and those to avoid. In a study assessing its predation behaviour, different prey species, with or without chemical defenses were provided to the beetles. The Streaked bombardier beetles (Brachinus sclopeta, Frabricius, 1792) for instance, release olfactory signals as warning of their toxicity to the predators when threatened. Compared to other prey species without chemical defenses, the Devil’s coach beetles attacked the Streaked bombardier beetles less frequently, suggesting that its ability to avoid dangerous prey through chemical signals detection.Their ability to assess the dangerousness of potential prey, along with their fierce movement for capturing fast-moving targets makes them highly effective hunters.
Despite its intimidating name, the Devil’s coach horse beetle is actually beneficial to people at its native range (i.e. Europe and Africa) as it consumes a lot of agricultural « pests ». This species, just like many others in nature, serves important ecological roles. We look forward to your visit to the Hong Kong Biodiversity Museum and share more interesting stories with you.
Text: Bonnie
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